PETpla.net Insider 12 / 2020

PREFORM PRODUCTION PETplanet Insider Vol. 21 No. 12/20 www.petpla.net 14 Ultra Hot Runners and automated Self-Cleaning Technology cuts downtime and boosts rPET preform quality Handling dust based on an article by Bilal El Sayed, PET Tooling Product Manager, Husky Every mould requires maintenance and cleaning, at some point; PET dust particles can naturally accumulate, over time, so this is inevitable. The hot runner must deliver molten PET to each cavity equally while maintaining melt consistency. If any plastic escapes into the hot runner the temperature degrades the melt and dust accumulates. This build-up of dust can lead to cavities going down. The cold half must allow the mould cavities to properly fill and form the desired parts. Moulds need vents large enough to allow air to escape but small enough to ensure that melt is retained. Over time, this makes vents prone to clogging with dust. Clogged vents result in trapped air, and trapped air can cause defects like shorts or voids. This is why it is so important for manufacturers to find successful ways to handle dust. Keeping moulds clean is even more important when running recy- cled PET (rPET). Using high amounts of rPET material can increase gas, powder and dust generation caused by residual contaminants, like AA blockers or O 2 scavengers, that per- sist in the recycling process. And as demand exceeds supply, it is possible for residual contaminants to increase and the quality of rPET to decline. With more and more brands looking to offer sustainable packaging solu- tions made using higher percentages of rPET, mould cleanliness becomes even more important. Increasing system speed compounds the impact of maintenance and cleaning on productivity: as cycle times reduce, moulds naturally create dust faster and require maintenance more often. How do producers solve this chal- lenge? It starts by working with a reliable and knowledgeable partner, who has the experience and expertise to develop and deliver leading-edge solutions. Why invest in Hot Runner technologies to clean dust when there exists a solution that can avoid it completely? Husky states to have gone further and offers proven solutions that mini- mise dust creation in the first place, thus helping to reduce down time, for scheduled and emergency mainte- nance. Solutions include Husky’s Ultra Hot Runner and patented Cold Half Self-Cleaning Technology, which are designed to eliminate dust and enable producers to move to rPET with more confidence and less risk. To reduce PET dust accumulat- ing where it should not, some PET mould manufacturers use vacuums to remove it in their hot runners. While vacuum technology may remove dust inside hot runners, it doesn’t change the amount that builds up in the cold half. This side will eventually need a thorough cleaning, causing downtime and lost productivity. Implementing an additional vacuuming step adds com- plexity and cost to an already compli- cated process. Husky’s Ultra Hot Runners have operated successfully by controlling and consistently delivering melt to each cavity. They prevent plastic from leaking, thus helping to prevent the generation of PET dust and eliminating the need for extra vacuum technology. Husky’s patented Ultra Spring technology uses a method called cold start protection, which keeps the nozzle and manifold sealed in a cold state before the hot runner reaches its operating temperature, thus reducing dust build-up in the stack. Addressing the root cause of dust creation eliminates the need for addi- tional mechanisms like vacuums and so reduces maintenance downtime. It also minimises component failure risk and, consequently, offers a significant advantage over those technologies that are susceptible to dust build up. What if a mould could clean itself? Until recently there have existed two common methods of neck ring vent cleaning: hand cleaning and dry ice blasting. While extremely effec- PREFORMS